The invention relates to a separable layer of permanently thermoplastic bonding material, to a laminate to a method for making same.
Separable layers of bonding material are used to secure cards such as check cards, credit cards, club membership cards or chip cards to a backing made of paper, cardboard or plastic. A further area of application for a separable layer of bonding material is lamination of a cling vinyl film onto a backing. The term “cling vinyl film” stands for an adhesive-free film which has been internally plasticized and thereby is self-adhesive, and which in printed form is attached to truck surfaces, for example, for advertising purposes.
To simplify the terminology, the object which is to be secured by a separable layer of bonding material to a backing will be referred to hereinafter as the information carrier. The following requirements are imposed on the separable layer of bonding material.
The bonding material must create, between information carrier and backing, a permanent composite bond which safely withstands further processing and distribution, is insensitive to climatic fluctuations and is aging-resistant.
It must be possible to detach the information carrier from the backing in a manner that is simple, convenient and guaranteed not to cause damage. Residues of bonding material must not remain on the information carrier.
The backing surface must no longer be tacky after detachment of the information carrier. The backing is often inserted into a file, and must not stick to it.
Pertinent separable adhesives are known in the literature as peelable glues. They are pressure-sensitive adhesives with low surface tackiness, especially polyacrylate solutions or dispersions, which may be partly cross-linked, and hot-melt adhesives, which bond firmly to the backing, which is usually made of paper, and can be peeled off from the back side of the information carrier, which is relatively resistant to splitting. The known adhesives do not always meet the cited requirements profile to a completely satisfactory degree.